Settlement of a Mat Foundation on a Thick Stratum of Sensitive Clay

1966 ◽  
Vol 3 (2) ◽  
pp. 102-103 ◽  
Author(s):  
L Casagrande
Keyword(s):  
Mat Foundation ◽  
Sensitive Clay ◽  
Thick Stratum

Settlement of Mat Foundation on Thick Stratum of Sensitive Clay

1965 ◽  
Vol 2 (4) ◽  
pp. 299-312 ◽  
Author(s):  
L Casagrande ◽  
P Firing ◽  
G Schoof ◽  
E John Tttrcke
Keyword(s):  
Groundwater Level ◽  
Industrial Plant ◽  
Effective Stresses ◽  
Preconsolidation Pressure ◽  
Load Increase ◽  
Order Of Magnitude ◽  
Mat Foundation ◽  
Building Load ◽  
Sensitive Clay ◽  
Thick Stratum

Foundation investigations for an industrial plant on a thick stratum of preconsolidated, sensitive clay are presented. In spite of the fact that the effective stresses in the clay caused by the building load remained below the average preconsolidation pressure of the clay, the settlement of the buildings locally appreciably exceeded the anticipated order of magnitude. It is shown that a drop in the groundwater level by a few feet would result in the effective stresses exceeding the preconsolidation pressure within the upper portion of the clay stratum. With such an assumption, the consolidation would not be governed by the very flat recompression branch of the consolidation curve, but in part also by the steep virgin compression branch of the consolidation curve. It is concluded that, when dealing with preconsolidated, sensitive clays, the total effective stresses caused by a proposed structure should be kept within a safe margin below the average preconsolidation pressure in order to make provision for any unforeseen load increase such as might arise from a drop in the groundwater elevation.

TWO-DIMENSIONAL LARGE DEFORMATION FINITE ELEMENT MODELLING OF SENSITIVE CLAY LANDSLIDES

2020 ◽  
Author(s):  
Bipul Hawlader ◽  
◽  
Chen Wang ◽  
Ripon Karmaker ◽  
Didier Perret ◽  
...  
Keyword(s):  
Finite Element ◽  
Large Deformation ◽  
Finite Element Modelling ◽  
Two Dimensional ◽  
Element Modelling ◽  
Sensitive Clay

Electroosmotic strengthening of soft sensitive clays

1991 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
K. Y. Lo ◽  
I. I. Inculet ◽  
K. S. Ho
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strength Increase ◽  
Sample Length ◽  
Voltage Distribution ◽  
Steady Current ◽  
Preconsolidation Pressure ◽  
Sensitive Clay ◽  
Pressure Stress

A comprehensive experimental investigation on the electroosmotic strengthening of soft sensitive clay was performed to assess the effectiveness of the treatment and to study the mechanism of the process. A specially designed electroosmotic cell was developed to prevent gas accumulation near the electrodes, to allow better electrode-soil contact, and to improve the treatment efficiency. This apparatus also enables the monitoring of the generated negative pore-water pressure along the sample length, settlement, voltage distribution, and current variation during treatment. The investigation covered two different types of soil trimmed at different orientations: the vertically and horizontally trimmed overconsolidated Wallaceburg clay and the vertically trimmed slightly overconsolidated soft sensitive Gloucester (Leda) clay. Results of this study showed that the voltage distribution and induced negative pore pressure at equilibrium along the sample are linear with steady current flow across the sample, indicating that the electrode design in the electroosmosis test apparatus is efficient. The electroosmotic consolidation curve is similar to that of the conventional consolidation curve, and the preconsolidation pressure was increased by 51–88% with an applied voltage up to 6 V. The undrained shear strength increased to a maximum of 172%, and the moisture content decreased by 30%. The technique of electrode reversal is employed, and a relatively uniform strength increase between the electrodes is observed. Key words: electroosmosis, electroosmotic cell, soft sensitive clay, negative pore-water pressure, preconsolidation pressure, stress–strain behaviour.

Time-Domain Nonlinear SSI Analysis of Foundation Sliding Using Frequency-Dependent Foundation Impedance Derived From SASSI

2008 ◽  
Author(s):  
Mansour Tabatabaie ◽  
Thomas Ballard
Keyword(s):  
Frequency Domain ◽  
Linear Systems ◽  
Time Domain ◽  
Soil Structure ◽  
Wave Radiation ◽  
Far Field ◽  
Frequency Dependent ◽  
Nonlinear Springs ◽  
Mat Foundation ◽  
The Time Domain

Dynamic soil-structure interaction (SSI) analysis of nuclear power plants is often performed in frequency domain using programs such as SASSI [1]. This enables the analyst to properly a) address the effects of wave radiation in an unbounded soil media, b) incorporate strain-compatible soil shear modulus and damping properties and c) specify input motion in the free field using the de-convolution method and/or spatially variable ground motions. For structures that exhibit nonlinearities such as potential base sliding and/or uplift, the frequency-domain procedure is not applicable as it is limited to linear systems. For such problems, it is necessary to solve the problem in the time domain using the direct integration method in programs such as ADINA [2]. The authors recently introduced a sub-structuring technique called distributed parameter foundation impedance (DPFI) model that allows the structure to be partitioned from the total SSI system and analyzed in the time domain while the foundation soil is modeled using the frequency-domain procedure [3]. This procedure has been validated for linear systems. In this paper we have expanded the DPFI model to incorporate nonlinearities at the soil/structure interface by introducing nonlinear shear and normal springs arranged in series between the DPFI and structure model. This combination of the linear far-field impedance (DPFI) plus nonlinear near-field soil springs allows the foundation sliding and/or uplift behavior be analyzed in time domain while maintaining the frequency-dependent stiffness and radiation damping nature of the far-field foundation impedance. To check the accuracy of this procedure, a typical NPP foundation mat supported at the surface of a layered soil system and subjected to harmonic forced vibration was first analyzed in the frequency domain using SASSI to calculate the target linear response and derive a linear, far-field DPFI model. The target linear solution was then used to validate two linear time-domain ADINA models: Model 1 consisting of the mat foundation+DPFI derived from the linear SASSI model and Model 2 consisting of the total SSI system (mat foundation plus a soil block). After linear alignment, the nonlinear springs were added to both ADINA models and re-analyzed in time domain. Model 2 provided the target nonlinear solution while Model 1 provided the results using the DPFI+nonlinear springs. By increasing the amplitude of the vibration load, different levels of foundation sliding were simulated. Good agreement between the results of two models in terms of the displacement response of the mat and cyclic force-displacement behavior of the springs validates the accuracy of the procedure presented herein.

Sign in / Sign up

Export Citation Format

Share Document